Self-energizing grip



y 1946. c. KANTNER, JR 2,400,514

" SELF-ENERGIZING GRIP Filed Feb. 24, 1944 1 I I I... f .12

- INVENTOR. LESLIE CKZNTNERk/R AGENT base of the machine to be at one side of the work piece W. A principal cylinder and piston mechanism |6 extends horizontally from the machine, and its piston rod carries a head l1. Links H! are pivotally connected with the head I1 and with the blocks l0. When the work piece W has been engaged in the grips A the cylinder and piston mechanisms l2 are operated to impose an initial stretch or tensile load on the work. The cylinder and piston mechanism I6 is then operated to cause the blocks In to rotate about their shafts II. This moves the jaws A and the ends of the work piece W toward the die l so that the work is stretched over the die to be contoured or shaped thereby. The present invention isnot primarily concerned with the details of the stretch-forming machine and such details are not believed essential to a full understanding of the invention.

The two grips A may be identical and I will proceed with a detailed description of one of them, it being understood that this description is equally applicable to the other grip.

The grip of the invention may be said to comprise generally a case 20, wedge jaws 2| and 22, and anti-friction means generally indicated at 23 mounting the jaws in the case 20 for free operation.

The case 20 forms the body of the grip and serves to house the jaws 2| and 22 and the means 23. The case '20 is of simple construction and comprises two plates 24 and two spaced side members 25 secured between the plates. The plates 24 are simple flat parts, the longitudinal edges of which are forwardly convergent. Channels or grooves 26 are provided in the inner faces of the plates 24 in spaced parallel relation to their convergent edges. Where the grips A are horizontally arranged as illustrated, the plates 24 form the top and bottom walls of thecase. The rear ends of the plates 24 have tongues 21 and the shackle I4 is received between the tongues. A vertical shaft 28 secures the shackle M to the tongues 21. The side membersr25 are thick-walled plate-like parts having fiat edges for contacting the inner sides of the plates 24. Tongues or keys 29 extend along these edges and fit the above referred to grooves 26. Series of cap screws 30 pass through openings in the plates 24 and are threaded into openings in the members 25 to connect the plates and members to form a box-like structure. The side members 25 are forwardly convergent, being flush with the above referred to convergent edges of the plates 24. The inner sides of the members 25 have machined or ground surfaces 3| to cooperate with the antifriction means 23. Inwardly projecting ledges or flanges 32 occur at the opposite ends of the finished surfaces 3|. seen that the case 20 is a simple readily assembled structure.

The jaws 2| and 22 are the active work engaging elements of the device. The jaws are in the nature of elongate wedge members whose inner sides are contoured or shaped to conform to the work piece W. The outer sides 33 of the jaws 2| and 22 areflat and are accurately machined to cooperate with the anti-friction means 23. The outer jaw surfaces 33 are pitched or have a wedge slope. I have found that the best results are obtained by giving the jaw surfaces 33 a wedge slope of twenty to one. The finished surfaces 3| of the case members 25 are correspondingly pitched to be parallel tothe surfaces 33. Figure 2 of the drawing illustrates the manner From the above it will be in which the pairs of opposing surfaces 3| and 33 are pitched with respect to the longitudinal axis of the grip.

The cross sectional contour or configuration of thejaws 2| and 22 depends upon the cross sectional shape of the work to be handled. In the particular case illustrated it may be considered that the work piece W is a simple part in the nature of an angle section. The male jaw 2| has on its inner side a longitudinally extending ridge 34 presenting inwardly convergent gripping surfaces adapted to engage in the angle sectioned work piece W. The female jaw 22 has a longitudinally extending groove 36 with outwardly convergent walls or surfaces for engaging with the outer surfaces of the work piece W. The ridge 34 and the groove 36 extend throughout the entire lengths of the jaws 2| and 22 and are uniform in shape. The surfaces presented by the ridge 34 and the groove 36 are related to evenly engage the surfaces of the work piece throughout the entire extent of the jaws.

The texture or character of the surfaces presented by the ridge 34 and groove 35 of the steel gripping jaws is an important feature of the invention. In preparing these surfaces they are first machined smooth and are then roughened to have a high coefficient of friction. I prefer to roughen theactive jaw surfaces by sand blasting them subsequent to all hardening and machining operations. This treatment of the active gripping jaw surfaces provides a uniformly high coefficient of friction throughout the entire extents of the surfaces. Figure 5 illustrates the slightly roughened or sand blasted surfaces S. the roughness being exaggerated. There are no distinct sizable projections, serrations or edges on the gripping surfaces S for concentrating the stresses in the work piece, but there is an infinite number of extremely small irregularities whichassure a full distribution of the stress throughout the entire surface areas. In actual practice the roughened surfaces S assure positive uniform ripping of the work W with no danger of failure by reason of stress concentrations. v

The antifriction means 23 is provided to reduce to a minimum the sliding friction accompanying actuation of the jaws 2| and 22. The means 23 isin the nature of a roller bearing means comprising two like or identical assemblies. A bearing assembly is arranged at the rear side of each gripping jaw. Each bearing assembly includes a cage or roll retainer comprising a pair of longitudinally extending members 31 engaged at their ends by spacers 38. Screws 33 may connect the members 31 and spacers 38. Spaced sockets or notches 40 are provided in the opposing faces of the cage members 31. The walls of the notches 40 are cylindrically curved and the diameter of curvature is greater than the thickness of the members 31. Anti-friction elements or rollers4| are arranged in the bearing cages to have their end portions received in the notches 40. The notches 40 serve to retain the rollers 4| in spaced generally parallel relation. The surfaces of the rollers 4| ride on the surfaces 3| of the case members 25 and cooperate with the rear surfaces 33 of the gripping jaws 2| and 22. The surfaces 3| and 33 are suitably hardened to prevent Brinelling by reason of the loads imposed by the rollers 4|. The bearing assemblies are floating. That is, they may advance and retract in the case 20 when the gripping jaws are operated and released- The flanges 32 on the members 25 serve to limit this free movement of thebearing assuming extreme forward positions prior to full actuation of the jaws and thus provide for ample .forward travel of the bearings during the gripping operation. The springs 42 assist in restoring the bearing to intermediate positions when the jaws 2| and 22 are released.

.In operation it will be assumed that the grips 'A of the invention are associated with the cylinder and piston mechanisms |2 of the stretchforming machine. When the work part W is to be stretch-formed its opposite end portions are introduced into the grips A. The work piece is readily inserted between thegripping jaws 2| and 22. The jaws 2| and 22 are normally free or released so that the work piece W may be easily entered between the active surfaces S of the jaws. When the cylinder and piston mechanisms |2 are operated the relative axial movement between the case 20 and the gripping jaws 2| and 22 results in actuation of the j aws. It will be seen that relative movement between the surfaces 3| and 33 causes inward actuation of the jaws bringing the jaw surfaces S into gripping engagement with the work piece W. The rollers 4| engaged between the wedge surfaces 3| and 33 reduce the sliding friction to a minimum and assure full rapid actuation of the gripping jaws. Thus with initial operation of the cylinder and piston mechanisms |2 the gripping jaws 2| and 22 are operated to grip the work piece W. The roughened jaw surfaces S have a high coeflicient of friction and obtain a work piece without concen- The uniformly distributed positive hold on, the trating the stresses.

gripping effect produced by the sand blasted sur-.

faces S permits the application of very high tensile loads to the work piece W without danger of fracturing the work. When the work piece W has been put under the required initial tension, the cylinder and piston mechanism I6 is operated to rotate the blocks l0 so that the work W is stretched about the die I5. The jaws 2| and 22 of the grips A retain their positive gripping engagement with the work piece W during the stretch-forming of the work. When the stretchforming operation has been completed and the work piece W is relieved of tension, the jaws 2| and 22 are released. The anti-friction rollers 4| provide for the ready release of the jaws.

By removing the shackle bolt 28, the jaws 2| and 22 may be inserted and removed through the rear of the case 20. It is to be understood that the jaws 2| and 22 may be replaced by jaws designed for the engagement of work pieces of various cross sectional configurations. The in vention provides efficient self energizing grips embodying readily replaceable gripping Having described only a typical form of the invention I do not wish to be. details herein set forth, but wish to reserve to myself any variations or modifications that may appear to those skilled in the art or fall within the scope of the following claims.

I claim: 5

I 1. A grip comprising a casing having a pair of gripping jaws adapted to grip the work, one of said jaws having a wedge-shaped ridge thereon, the other jaw having a correspondingly shaped groove therein to receive the ridge, said jaws being movable toward each other to cause the ridge to force the work into the groove to bindingly engage the same therein.

2. A device as claimed in claim 1 wherein the confronting surfaces of the ridge and groove are minutely roughened.

. LESLIE C. KANTNER, JR.

jaws equipped with highly .efficient gripping surfaces.

limited to the specific 

